The invention relates to an evaporator for a carbon dioxide air-conditioner for cooling using carbon dioxide as a refrigerant.
There have been proposed related heat exchangers and refrigeration cycle apparatuses (e.g., Japanese Patent Application Laid-open No. 2003-28539 (paragraphs 0035 to 0040, FIG. 1)). In the related art, an area of a refrigerant passage closer to a refrigerant outlet of an evaporator tube is set greater than an area of the refrigerant passage closer to a refrigerant inlet.
According to this setting, the speed of a refrigerant in the refrigerant passage closer to the refrigerant outlet is reduced, and a liquid phase refrigerant covering the refrigerant passage is prevented from being carried by a gas phase refrigerant. This suppresses so-called dryout in the refrigerant passage closer to the refrigerant outlet, and enhances the heat exchange efficiency.
The invention is directed to provide an evaporator for a carbon dioxide air-conditioner preventing lubricant oil separated from a refrigerant from accumulating in a header tank.